var obj = {
  name: 'zhangsan',
  age: 12,
  sayHello: function () { console.log('hello'); }
}
var res = obj.toString()
// console.log("gender" in obj)
// console.log(res)
console.log(obj.hasOwnProperty('toString')); //false
console.log("toString" in obj) //toString是继承的属性和方法
